1. Field of The Invention
This invention relates to the art of forming tunnel liners and particularly to improvements for forming such tunnel liners with panels of arched sheet-metal material, and includes a unique method of building such tunnel liners and unique panels and assemblies of panels.
2. Background And Prior Art
Machines which form bendable materials, such as sheet-metal, into panels and curve the panels for making continuous arched buildings or roofs for buildings by seaming the panels together are known in the art. Such machines are commercially available from M.I.C. Industries, Inc., of Reston, Va. and are shown, at least partially, in U.S. Pat. Nos. 3,842,647, 3,902,288, 3,967,430, and 4,364,253, all owned by M.I.C. Industries, Inc., the present assignee. In this prior art, the panels formed from sheeted steel or the like are used with a seaming apparatus which operates from the top of the structure to seam adjacent panels and to secure these panels together.
A problem exists with the prior art described above when attempting to construct a structure within a closed space, such as a lining for a tunnel, or when a distance between the top of the panels and the existing structure is so limited that seaming cannot be accomplished.
U.S. Pat. No. 5,393,173, also owned by M.I.C. Industries, Inc., shows a tunnel liner building method and building panels therefor that among other things overcame certain problems in the above-noted prior art. The '173 patent teaches the formation of tunnel liners from panels of arched, bendable sheet material. In the '173 patent, panels 10 include a central portion 12, inclined side portions 14 and 16, wing portions 18 and 20, and a hook portion 22 and a receptacle portion 28 at opposite sides of each panel 10. In the '173 patent, the panels can be joined with the hook portion of one panel fitting into the receptacle portion of the other panel and then continuously seamed from the underside, i.e., the inside of the arched assembly.
There are, however, limitations in the '173 device, and there exists a need for an improved tunnel liner building method and building panels therefor. Among other limitations, the seaming method of the '173 patent can result in difficulties during assembling.